MOM : "Don't forget to pick up the brass when you're done shooting your Garand, OK?"
ME : "Whatever. Not like we have a reloading kit or something..."

LIMEY : "That bitch was brass mate!"

DRUG-DEALER : "No brass, no deal. Now get outta here."

AUSSIE : "Ah'll brass that bitch up mate!"

LIEUTENANT : "The operation was a success!"
COLONEL : "I noticed. I'm gonna bring it up with the Brass later on. Hope they accept the results though....you know how nervous and picky the Brass can be."

I am pretty sure that the top comment is correct, it does mean prostitute in cockney rhyming slang but I read somewhere that it comes from people saying brass flute for prostitute which makes more sense to me then brass nail.